title: Real-time measurement of ArF excimer laser corneal tissue ablation rates using cross-correlation of laser waveforms.
abstract: The current popularity of excimer laser refractive surgery suggests a need for continued research and refinements to further improve clinical outcomes. A fundamental limitation of current clinical systems is the lack of real-time feedback specifically addressing the laser-tissue interactions as directly related to laser ablation rates. This paper reports data to assess the feasibility of a novel approach that holds promise as a real-time feedback scheme based on comparison of the incident and reflected laser pulse waveforms, as quantified using a cross-correlation algorithm. The approach is evaluated for ablation of bovine cornea over a range of clinically relevant laser fluences. A linear relationship was observed between several cross-correlation metrics and the directly measured corneal ablation rate, yielding an average RMS predictive error of 3.9% using a 25-shot average reflected waveform. Assessment of the cross-correlation approach for single-shot ablation data revealed a brief transient corresponding to the first few laser pulses, which is attributed to a slight hydration gradient near the surface of the de-epithelialized cornea. Clinical refractive data are necessary to assess the precision of this approach for actual refractive surgery.
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Florida, Gaiensville, FL 32611, USA. btfishe@sandia.gov
authors.forename: Brian T
authors.initials: BT
authors.lastname: Fisher
authors.forename: David W
authors.initials: DW
authors.lastname: Hahn
mesh_terms: D000818:Animals; D002417:Cattle; D003199:Computer Systems; D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D054018:Lasers, Excimer